Electronically commutated single-phase motor

ABSTRACT

The present invention refers to an electronically commutated single phase motor comprising a rotor ( 2; 202; 302 ) and a stator ( 3; 203; 303 ) with an asymmetrical wound yoke ( 4; 204; 304 ) and comprising at least a stator phase ( 5; 205; 305 ) energized via an electronic commutation circuit in accordance with a driving signal generated by sensor means ( 8; 208; 308 ) for detecting the angular position of said rotor ( 2; 202; 302 ); said sensor means ( 8; 208; 308 ) comprise at least an inductive coil ( 9; 209; 219; 309 ) that is coupled magnetically to said rotor ( 2; 202; 302 ) and is arranged at substantially 90 electrical degrees with respect to said stator phase ( 5; 205; 305 ); the inductive coil ( 9; 209; 219; 309 ) and the stator phase ( 5; 205; 305 ) are arranged adjacent to each other and are wound round axes that are substantially parallel to each other.

The present invention refers to an electronically commutatedsingle-phase motor comprising a rotor, a stator with asymmetric woundyoke, and sensor means to detect the angular position of the rotor.

The Italian patent no. 1268400, granted on 27^(th) Feb. 1997 to thissame Applicant following an application filed on 30^(th) Mar. 1994,which shall be intended as being incorporated herein by reference in itsentirety, describes an electronically commutated motor comprising aferromagnetic or permanent-magnet rotor and a wound stator comprising atleast a stator phase that is energized via an electronic-commutationcircuit in accordance with a driving signal generated by sensor meansdetecting the angular position of the rotor. These sensor means comprisean inductive coil that is magnetically coupled with the rotor andarranged at 90 electrical degrees with respect to the stator phase, sothat the driving signal is induced in the sensor with a correspondingphase shift with respect to the voltage induced in the stator phase.

Although the above-described technical solution has been found to beparticularly advantageous, it nevertheless may involve significantcomplications from an industrial engineering point of view, inparticular as far as the sensor means are concerned, in view a massproduction of the motors in which it is implemented.

The application of the sensor means described in the afore-cited patentpublication to a single-phase motor provided with an asymmetrical, e.g.U-shaped stator yoke implies further construction-related andoperation-related complications: the sensor means would in fact bepositioned in the most advantageous manner quite close to the rotor, butfar enough from the coils of the main winding in order to avoid theelectromagnetic flux generated by these coils; however, such apositioning of the sensor means implies that the terminals connectingthe coils and the sensor means to the electronic circuit-board be placedat a distance from each other thereby causing them to be quite difficultand inconvenient to be connected to said electronic circuit-board.

In this application, the need furthermore arises for the arrangement ofthe sensor means at 90 electrical degrees with respect to theelectromagnetic flux generated by the coils of the main winding to bestrictly ensured in view of enabling a correct detection of the angularposition of the rotor to be obtained: an arrangement of the sensor meanson the stator yoke close to or at the top portion of the flanks of the“U”, which would actually prove as the ideal arrangement for said sensormeans, since they would be lying close to the rotor and distant from thecoils (the turns of which are wound about each one of the shanks of the“U”), is not sufficient by itself to reliably ensure a correctpositioning thereof owing to possibly existing misalignments of the topportions of the same flanks.

It therefore is the object of the present invention to provide asolution for the construction of an electronically commutatedsingle-phase motor with asymmetrical yoke, and comprising sensor meansfor the detection of the angular position of the rotor, which proves tobe particularly advantageous as far as both the construction and theoperation effectiveness of the same motor are concerned.

Within this general object, it is a purpose of the present invention toprovide a motor of the above-indicated kind, in which the arrangement ofthe sensor means proves ideal in view of both a correct detection of theangular position of the rotor and a convenient connection of theterminals thereof to the electronic circuit board.

Another purpose of the present invention is to provide a motor of theabove-indicated kind, in which the arrangement of the sensor means at 90electrical degrees with respect to the electromagnetic flux generated bythe coils of the main winding is effectively ensured in view ofobtaining a correct detection of the angular position of the rotor.

Another purpose yet of the present invention is to provide a motor ofthe above-indicated kind, which does not require any substantialmodification to be introduced in coiling machines in view of making themable to produce the inductive coils of both the main coils and thesensor means.

Finally, an equally important purpose of the present invention is toprovide a motor of the above-indicated kind, which is capable of beingproduced competitively from a cost-related point of view, using readilyavailable machines, tools and techniques.

According to the present invention, these aims and advantages, alongwith further ones that will emerge from the following description, arereached in an electronically commutated single-phase motor comprising arotor, an asymmetrical stator yoke and sensor means for detecting theangular position of the rotor incorporating the features andcharacteristics as recited in the appended claim 1.

Features and advantages of the present invention will anyway be morereadily understood from the description of some preferred, although notsole embodiments that is given below by way of non-limiting example withreference to the accompanying drawings, in which:

FIG. 1 is front view of a motor according to the present invention;

FIGS. 2 and 3 are front views showing schematically the directions ofthe fluxes generated by the stator yoke and the rotor, respectively, inthe motor appearing in FIG. 1;

FIG. 4 is a perspective view of the bobbin for the main winding of themotor illustrated in the preceding Figures, in the initial configurationthereof after moulding;

FIG. 5 is a perspective view of the bobbin shown in FIG. 4, in theintermediate configuration that is takes during coiling of the sensormeans;

FIG. 6 is a perspective view of the bobbin shown in FIG. 4, in the finalconfiguration taken by it during coiling of the sensor means;

FIGS. 7 and 8 are perspective views of a different embodiment of thebobbin, in an intermediate configuration and a final configurationthereof, respectively;

FIG. 9 is a front view of a second embodiment of the motor according tothe present invention;

FIG. 9 a is a schematical view of the coiling direction of the mainwinding and the coil of the sensor, respectively, of the secondembodiment shown in FIG. 9;

FIGS. 10 through to 12 are perspective views of a third embodiment ofthe motor according to the present invention;

FIG. 13 is a front view of the motor shown in the preceding Figures.

With reference to the above-noted Figures, the reference numeral 1 isgenerally used there to indicate an electronically commutatedsingle-phase motor, which comprises a rotor 2 and a stator 3 with anasymmetrical yoke 4 in the shape of substantially a U and comprising atleast a stator phase 5, which in the example of embodiment illustratedin FIG. 1 is comprised of two main inductive windings 6 and 7 and isenergized via an electronic commutation circuit in accordance with adriving signal generated by sensor means 8 detecting the angularposition of the rotor 2.

Said sensor means 8 comprise an inductive coil 9 that is coupledmagnetically to the rotor 2 and is arranged at an angle of substantially90 electrical degrees with respect to the stator phase 5.

According to an innovatory feature of the present invention, theinductive coil 9 is arranged adjacent to the stator phase 5 and,therefore, to the main inductive windings 6, 7, and is wound round anaxis X that is substantially parallel to the axes Y and Z, about whichsaid main inductive windings 6 and 7 are wound.

In order to obtain said arrangement at 90 electrical degrees through theabove-indicated configuration, the main windings 6 and 7 coiled roundthe two shanks of the U formed by the stator yoke 4 have mutuallyopposed directions, in such a manner as to generate a magnetic fieldwith an orientation of the flux A as indicated in FIG. 2, whereas thecoil 9 of the sensor means 8, which is placed between the two mainwindings 6 and 7, is wound in a single direction so that its flux canlink with the leakage fluxes B generated by the magnet of the rotor 2,as this is shown schematically in FIG. 3.

Through the above-indicated arrangement, the magnetic field generated bythe main windings 6, 7 does not link with the coil 9, whereas themagnetic field generated by the magnet of the rotor 2 is able to linkwith the coil 9, which therefore operates as if it were a coil arrangedat 90 electrical degrees with respect to the main windings.

To act as a support for both the main windings 6 and 7 and the coil 9 ofthe sensor means 8 (hereinafter referred to simply and shortly as“sensor 8”) there is provided a bobbin 10 adapted to be associated tothe stator yoke 4.

With reference to FIGS. 4 through to 6, the bobbin 10 comprises a firstand a second support member 11, 12 for the main inductive windings 6, 7,said support members having a first pair of headpieces 13, 14 and asecond pair of headpieces 15, 16, respectively, at the extremitiesthereof; the headpieces 13 and 15 and the headpieces 14 and 17 arearranged side-by-side and substantially co-planar with respect to eachother.

To complete the bobbin 10 there is further provided a third supportmember 18 for the coil 9 of the sensor 8, which is associated, or iscapable of being associated, to the respective headpieces 13 and 15 ofthe first and second support members 11, 12.

In an advantageous manner, the bobbin 10 is formed as a moulded part ofa thermoplastic material in the initial configuration illustrated inFIG. 4, in which the first and second support members 11, 12 are facingeach other and connected to each other at the respective headpieces 14and 16 thereof via an elastically bendable connection member 17, whereasthe headpieces 13 and 15 on the opposite side are separate from eachother.

In the particular embodiment illustrated in FIGS. 4 to 6, the thirdsupport member 18 is comprised of at least two profile sections 18 a, 18b having, at least along two separate and distinct lengths thereof, apreferably T-shaped cross-section, in which the shank of the T forms thesupport for the coil, whereas the beam or cross-bar of the T is theheadpiece. The profile sections 18 a, 18 b are associated to theheadpiece 13 and the headpiece 15, respectively, and are made integral,i.e. as a single-piece construction with the bobbin 10 during themoulding operation. The mutually facing surfaces of the cross-bars ofthe T's are advantageously in abutting contact with each other so as toprovide greater stability to the bobbin 10, as well as to ensure thecorrect positioning of the sensor 8 at 90 electrical degrees withrespect to the stator phase 5.

From the initial configuration thereof shown in FIG. 4, the bobbin 10 isopened through the rotation of the first and second support members 11,12 about the elastic hinge formed by the connection member 17, until theheadpiece 16 comes into contact with the headpiece 14. The bobbin 10comes in this way to take an intermediate configuration, which is bestillustrated in FIG. 5 and is particularly adapted to allow for thecoiling of the main windings 6, 7 to be carried out simultaneously. Assoon as this coiling operation is concluded, the bobbin 10 is closedagain through the rotation of said support members in the oppositedirection with respect to the previous one, until it comes to take thefinal configuration illustrated in FIG. 6. The coil 9 of the sensor 8 isat this point wound round the third support member 18. Upon completionof this operation, the same coil 9 cooperates to keep the bobbin 10closed.

FIGS. 7 and 8 illustrate a different embodiment of the bobbin, in whichthe third support member 118 is obtained separately from the firstsupport member 111 and the second support member 112; once the mainwindings have been coiled in the above-described manner, the thirdsupport member 118 is connected to the bobbin 110 at the headpieces 113and 115 thereof, with the aid of connection means known as such in theart, such as for instance by snap-fitting appropriate links 119belonging to the third support member 118 into slits 120 provided in theheadpieces 113, 115, or with the use of suitable bonding, welding,riveting or similar techniques known as such in the art.

Fully apparent from the above description is therefore the ability ofthe the present invention to effectively reach the afore cited aims andadvantages by actually providing a solution for the construction of anelectronically commutated single-phase motor, in which the arrangementof the sensor means 8 is the optimum one as far as both the correctdetection of the angular position of the rotor 2 and the connection ofthe terminals of the windings 6, 7, 9 to the electronic circuit-board(not shown) are concerned. In fact, thanks to the particular arrangementof the respective windings, the magnetic field generated by the statorphase 5 does not interfere with the sensor 8, whose coil 9 is solelylinked with the magnetic field generated by the rotor 2; the mutuallyadjacent arrangement of the stator phase 5 and the sensor 8 doestherefore not affect the correct detection of the angular position ofthe rotor 2, while at the same time allowing for the arrangement of thewindings in such a manner as to enable the terminals thereof to lieclose to each other in view of a convenient connection thereof to theelectronic circuit-board.

In addition, the positioning of the sensor means at 90 electricaldegrees with respect to the electromagnetic flux generated by the coilsof the main winding is ensured also physically, thanks to the thirdsupport member 18, 118 being so provided as to rest directly on both thefirst and the second support members 11, 12, 111, 112: such acontrivance is effective in considerably reducing the possibility formisalignments to occur between the main winding and the sensor coil.

The motor according to the present invention proves furthermoreparticularly advantageous from a manufacturing point of view: windingand coiling operations can in fact be performed in an extremelyconvenient and quick manner without any need arising for conventionalwinding machines to be modified to any substantial extent, thanks to theconformation of the bobbin 10, 110 adapted to support both the mainwinding and the sensor coil.

It will of course be appreciated that the present invention, asdescribed above, may be subject to a number of modifications or may beembodied in a number of different manners without departing from thescope of the invention.

So, for instance, FIG. 9 can be notices to illustrate a secondembodiment of the present invention, in which the reference numeral 201is generally used there to indicate an electronically commutatedsingle-phase motor, which comprises a rotor 202 and a stator 203 with anasymmetrical yoke 204 in the shape of substantially a U and comprisingat least a stator phase 205, which is comprised of a first and a secondmain inductive windings 206 and 207 and is energized via an electroniccommutation circuit in accordance with a driving signal generated bysensor means 208 detecting the angular position of the rotor 202.

Said sensor means 208 comprise a third and a fourth inductive coils 209,219 that are coupled magnetically to the rotor 202 and are arranged atan angle of substantially 90 electrical degrees with respect to thestator phase 205.

Said third and fourth inductive coils 209, 219 are arranged adjacent tothe stator phase 205 and, therefore, to the main inductive windings 206,207, and are wound round axes that are substantially coinciding with theaxis X of the first winding 206 and the axis Y of the second winding207, respectively, which are arranged substantially parallel to eachother.

In order to obtain said arrangement at 90 electrical degrees through theabove-indicated configuration, the main windings 206 and 207 wound roundthe two shanks of the U formed by the stator yoke 204 are magneticallyconcordant with respect to the stator yoke 204 and the main magneticflux, whereas the coils 209, 219 of the sensor means 208 aremagnetically discordant with respect to said same stator yoke 204 andmain magnetic flux, so that their fluxes can link with the leakagefluxes generated by the magnet of the rotor 202.

Represented schematically in FIG. 9 a are the arrangements of the mainwindings 206, 207 and the coils 209, 219 of the sensor 208 relative tothe stator yoke 204; the reference letters I and F are used to indicatethe beginning and the end of the main windings 206, 217, whereas thereference letters Is and Fs are used to indicate the beginning and theend of the coils 209, 219.

With the above-indicated arrangement, the magnetic field generated bythe main windings 206, 207 nullifies on the coils 209, 219 of the sensormeans 208, whereas the magnetic field generated by the magnet of therotor 202 sums up on said coils 209, 219, which therefore act as if theywere a single coil arranged at 90 electrical degrees with respect to themain windings.

To act as a support for said windings and coils 206, 207, 209, 219 thereis provided a bobbin 210 adapted to be associated to the stator yoke204, and comprising a first and a second support member 211, 212 for themain inductive windings 206, 207, as well as a third and a fourthsupport member 218, 220 for the coils 209, 219 of the sensor means 208,which are separated from each other by respective headpieces 213, 214,respectively. As far as the aspects connected with the production ofthis bobbin 210 are concerned, as well as the manner in which it works,reference should be made to the related description given afore inconnection with the bobbins 10, 110.

FIGS. 10 to 13 illustrate a third embodiment of the motor according tothe present invention, in which the third support member 318 for theinductive coil 309 of the sensor means 308 is associated to a casing 321for the rotor 302, instead of being associated to the bobbin 310 as inthe previously described embodiments. The third support member 318 maybe connected to the casing 321 by any of a number of known connectionmeans or may be obtained integrally, i.e. as a single-piececonstruction, with the same casing 321.

Once the coiling operation of the main windings 306 and 307 is completedin the afore-described manner, and once the coil 309 of the sensor means308 has been wound round the third support, member 318, the casing 321with the coil 309 associated thereto is introduced in the stator yoke304, so as illustrated in FIG. 11, thereby obtaining the arrangementshown in FIGS. 12 and 13.

It should be noticed that the materials used, as well as the shapes andthe sizing of the individual items of the motor of the invention, mayeach time be selected so as to more appropriately meet the particularrequirements or suit the particular application.

1. Electronically commutated single-phase motor comprising a rotor (2;202; 302) and a stator (3; 203; 303) with an asymmetrical wound yoke (4;204; 304) and comprising at least a stator phase (5; 205; 305) energizedvia an electronic commutation circuit in accordance with a drivingsignal generated by sensor means (8; 208; 308) for detecting the angularposition of said rotor (2; 202; 302), said sensor means (8; 208; 308)comprising at least an inductive coil (9; 209; 219; 309) that is coupledmagnetically to said rotor (2; 202; 302) and is arranged atsubstantially 90 electrical degrees with respect to said stator phase(5; 205; 305), characterized in that said at least an inductive coil (9;209; 219; 309) and said stator phase (5; 205; 305) are arranged adjacentto each other and are wound round axes that are substantially parallelto each other.
 2. Motor according to claim 1, in which said stator yoke(4; 204; 304) has two arms round which there is wound said stator phase(5; 205; 305) comprising two main windings (6, 7; 206, 207; 306, 307).3. Motor according to claim 2, in which said main windings (6, 7; 306,307) and said coil (9; 309) of said sensor means (8; 308) are wound in amanner that said coil (9; 309) links with the magnetic field generatedby said rotor (2; 302) and does not link with the magnetic fieldgenerated by said main windings (6, 7; 306, 307).
 4. Motor according toclaim 2, in which said main windings (6, 7; 206, 207; 306, 307) and saidcoil (9; 209; 219; 309) of said sensor means (8; 208; 308) are supportedby a bobbin (10; 110; 210; 310) adapted to be associated to said statoryoke (4; 204; 304).
 5. Motor according to claim 4, in which said bobbin(10; 110; 210; 310) is comprised of a first and a second support member(11, 12; 111, 112; 211, 212) for said main inductive windings (6, 7;206, 207; 306, 307), said support members having a first pair ofheadpieces (13, 14; 113, 114; 213, 214) and a second pair of headpieces(15, 16; 115, 116; 215, 216), respectively, at the extremities thereof,said respective pairs of headpieces being arranged side-by-side andsubstantially co-planar with respect to each other.
 6. Motor accordingto claim 5, in which said bobbin (10) is further provided with a thirdsupport member (18; 218, 220) for said coil (9; 209; 219) of said sensormeans (8; 208), which is associated, or is capable of being associated,to the respective headpieces (13, 15; 113, 115; 213, 215) of said firstand said second support members (11, 12; 111, 112; 211, 212).
 7. Motoraccording to claim 6, in which said third support member (18; 118, 218,220) is obtained integrally with said bobbin (10; 210).
 8. Motoraccording to claim 6, in which said third support member (118) isconnected to said bobbin (110).
 9. Motor according to claim 1, in whichsaid sensor means (208) comprise a third and a fourth inductive coils(209, 219) that are coupled magnetically to said rotor (202) and arearranged at substantially 90 electrical degrees with respect to saidstator phase (205).
 10. Motor according to claim 9, in which said thirdand fourth inductive coils (209, 219) are arranged adjacent to saidstator phase (205) and, therefore, to said main inductive windings (206,207), and are wound round respective axes that are substantiallycoinciding with the axis (X) of said first winding (206) and the axis(Y) of said second winding (207), respectively, said axes (X, Y) beingsubstantially parallel to each other.
 11. Motor according to claim 10,in which said main inductive windings (206, 207) and said third andfourth inductive coils (209, 219) of said sensor means (208) are woundin a manner that they are magnetically concordant and magneticallydiscordant, respectively, with respect to said stator yoke (204) and themain magnetic flux.
 12. Motor according to claim 11, in which saidbobbin is provided with a third and a fourth support member (218, 220)for said third and forth coils (209, 219), respectively, of said sensormeans (208), which are separated from each other by respectiveheadpieces (213, 214).
 13. Motor according to claim 1, in which saidthird support member (318) for said inductive coil (309) of said sensormeans (308) is associated to a casing (321) for said rotor (302). 14.Motor according to claim 13, in which said third support member (318) isconnected to said casing (321) by any of a number of known connectionmeans
 15. Motor according to claim 13, in which said third supportmember (318) is formed integrally with said casing (321).
 16. Motoraccording to claim 13, in which said casing (321), with said coil (309)associated thereto, is introduced in said stator yoke (304) fitted withsaid main windings (306, 307).
 17. Motor according to claim 2, in whichsaid sensor means (208) comprise a third and a fourth inductive coils(209, 219) that are coupled magnetically to said rotor (202) and arearranged at substantially 90 electrical degrees with respect to saidstator phase (205).
 18. Motor according to claim 3, in which said sensormeans (208) comprise a third and a fourth inductive coils (209, 219)that are coupled magnetically to said rotor (202) and are arranged atsubstantially 90 electrical degrees with respect to said stator phase(205).
 19. Motor according to claim 4, in which said sensor means (208)comprise a third and a fourth inductive coils (209, 219) that arecoupled magnetically to said rotor (202) and are arranged atsubstantially 90 electrical degrees with respect to said stator phase(205).
 20. Motor according to claim 5, in which said sensor means (208)comprise a third and a fourth inductive coils (209, 219) that arecoupled magnetically to said rotor (202) and are arranged atsubstantially 90 electrical degrees with respect to said stator phase(205).